This invention relates to isotopic separation processes for uranium, and more particular to a method for producing a beam of neutral uranium atoms by vaporizing uranium from a uranium containing compound.
The separation of the isotope U.sup.235 (which is fissionable by neutrons) from natural uranium, a binary mixture containing mainly non-fissionable U.sup.238, or simply the enrichment of the mixture in U.sup.235 are extremely important processes for nuclear applications. The process now used on an industrial scale is the separation by diffusion through a porous barrier, although a number of other processes have been used or suggested including electromagnetic separation (the so-called "calutron" separation), separation by centrifugation, and by thermal diffusion.
More recently isotopic separation by laser has been proposed wherein uranium vapor is irradiated by laser light to preferentially excite the U.sup.235 isotope, as exemplified by U.S. Pats. No. 3,443,087, issued May 6, 1969 and No. 3,558,877, issued Jan. 26, 1971, and by French Patent No. 2,094,967 published Apr. 2, 1972.
Isotopic separation by laser light requires a source of neutral uranium atoms "intense" enough to provide a uranium vapor pressure of about 10.sup.-.sup.2 torr for periods of several hours. Conventional beam sources, in which uranium metal is resistively heated in a tungsten boat, are not practical for this purpose since molten uranium is highly corrosive to tungsten. At 2000.degree.K, where the uranium vapor pressure is barely adequate, a tungsten boat will last only a few minutes. Arc-melting and electron-beam melting are not desirable because these methods create uranium atoms in an excited state rather than the required neutral atoms. Also, a prior known process for producing a beam of neutral uranium atoms, described in J. Chem. Phys., Sept. 1, 1972, page 1975, involved an atom beam source in which uranium metal is vaporized from a tungsten filament.